1. Field of the Invention
The present invention relates to testing of network devices such as integrated network switches configured for switching data packets between subnetworks.
2. Background Art
Local area networks use a network cable or other media to link stations on the network. Each local area network architecture uses a media access control (MAC) enabling network interface devices at each network node to access the network medium.
Switched local area networks such as Ethernet (IEEE 802.3) based systems are encountering increasing demands for higher speed connectivity, more flexible switching performance, and the ability to accommodate more complex network architectures. For example, commonly-assigned U.S. Pat. No. 5,953,335 discloses a network switch configured for switching layer 2 type Ethernet (IEEE 802.3) data packets between different network nodes. Hence, network switch designers and test engineers need to be able to minimize the time and expense needed to evaluate designs during prototyping of Ethernet-based network systems.
One problem associated with testing network-based switch chips involves testing the various functions associated with the switch operation. In particular, the network switch disclosed in U.S. Pat. No. 5,953,335 discloses transmission of data packets in full-duplex mode according to the proposed Ethernet standard IEEE 802.3x Full-Duplex with Flow Controlxe2x80x94Working Draft (0.3). The full-duplex environment provides a two-way, point-to-point communication link between each network station and the switch, where the switch and the respective stations can simultaneously transmit and receive data packets without collisions. Hence, two or more stations can simultaneously transmit and receive Ethernet data packets between each other via a switched hub without collisions.
Flow control has been proposed to reduce network congestion, where a sending station temporarily suspends transmission of data packets. A proposed flow control arrangement for a full duplex environment, referred to as IEEE 802.3x[2], specifies generation of a flow control message, for example a PAUSE frame. A transmitting station that receives the PAUSE frame enters a pause state in which no frames are sent on the network for a time interval specified in the PAUSE frame.
Unfortunately, there is no recognized procedure for testing the response of a transmitting station (e.g., a transmitting port on a network switch) to reception of a flow control frame.
There is a need for an arrangement that tests the response of an integrated network device, such as an integrated network switch, to the reception of flow control frames.
These and other needs are attained by the present invention, where an arrangement for testing flow control logic in an integrated network device such as a network switch includes a traffic generator configured for transmitting pause frames having prescribed pause values. The network device is configured for continuously transmitting data frames on a network medium. The traffic generator is configured for outputting a first pause frame to the network device that specifies a first pause interval, followed by outputting during the first pause interval a second pause frame specifying a second pause interval substantially less than the first pause interval. The traffic generator is configured for measuring a time interval between transmission of the first pause frame and reception of subsequent data frames from the network device for evaluation of the flow control logic. Hence, the traffic generator can determine whether the second pause frame causes the flow control logic to cancel the first pause frame.
One aspect of the present invention provides a method. The method includes configuring a network device having flow control logic for continuously transmitting data frames on a network medium. The method also includes outputting by a traffic generator a first pause frame onto the network medium, the first pause frame specifying a first pause interval. The method also includes second outputting by the traffic generator and within the first pause interval a second pause frame onto the network medium, the second pause frame specifying a second pause interval substantially less than the first pause interval. A time interval between transmission of the first pause frame and reception of subsequent data frames from the network device also is measured by the traffic generator for evaluation of the flow control logic.
Another aspect of the present invention provides a test system having a network device and a traffic generator. The network device has flow control logic configured for suspending transmission of data frames onto a network medium in response to detection of a pause frame specifying a pause interval, and the network device is configured for continuously transmitting data frames onto the network medium for testing of the flow control logic. The traffic generator is configured for outputting a first pause frame to the network device that specifies a first pause interval, followed by outputting during the first pause interval a second pause frame specifying a second pause interval substantially less than the first pause interval. The traffic generator also is configured for measuring a time interval between transmission of the first pause frame and reception of subsequent data frames from the network device for the testing of the flow control logic.
Additional advantages and novel features of the invention will be set forth in part in the description which follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The advantages of the present invention may be realized and attained by means of instrumentalities and combinations particularly pointed in the appended claims.